extractURLParameterNames.cpp

#include <Functions/FunctionFactory.h>
#include <Functions/FunctionTokens.h>

namespace DB
{

namespace
{

using Pos = const char *;

class ExtractURLParameterNamesImpl
{
private:
    Pos pos;
    Pos end;
    bool first;

public:
    static constexpr auto name = "extractURLParameterNames";

    static bool isVariadic() { return false; }
    static size_t getNumberOfArguments() { return 1; }

    static ColumnNumbers getArgumentsThatAreAlwaysConstant() { return {}; }

    static void checkArguments(const IFunction & func, const ColumnsWithTypeAndName & arguments)
    {
        FunctionArgumentDescriptors mandatory_args{
            {"URL", &isString<IDataType>, nullptr, "String"},
        };

        validateFunctionArgumentTypes(func, arguments, mandatory_args);
    }

    static constexpr auto strings_argument_position = 0uz;

    void init(const ColumnsWithTypeAndName & /*arguments*/, bool /*max_substrings_includes_remaining_string*/) {}

    /// Called for each next string.
    void set(Pos pos_, Pos end_)
    {
        pos = pos_;
        end = end_;
        first = true;
    }

    /// Get the next token, if any, or return false.
    bool get(Pos & token_begin, Pos & token_end)
    {
        if (pos == nullptr)
            return false;

        if (first)
        {
            first = false;
            pos = find_first_symbols<'?', '#'>(pos, end);
        }
        else
            pos = find_first_symbols<'&', '#'>(pos, end);

        if (pos + 1 >= end)
            return false;
        ++pos;

        while (true)
        {
            token_begin = pos;

            pos = find_first_symbols<'=', '&', '#', '?'>(pos, end);
            if (pos == end)
                return false;
            else
                token_end = pos;

            if (*pos == '?')
            {
                ++pos;
                continue;
            }

            break;
        }

        return true;
    }
};

using FunctionExtractURLParameterNames = FunctionTokens<ExtractURLParameterNamesImpl>;

}

REGISTER_FUNCTION(ExtractURLParameterNames)
{
    factory.registerFunction<FunctionExtractURLParameterNames>();
}

}